Artificial hip implantation
has become increasingly common, particularly for younger, active patients who
have suffered significant osteoarthritis in their hips. While the five-year
survival rate following hip replacement is above 95 percent, recent device
failures, implant recalls and instances of chromium and cobalt toxicity as well
as other, serious hip implant problems have plagued the artificial hip
industry. The number of pseudotumors occurring in those with artificial hips is
increasing, particularly in all-metal implants or designs which implement metal
neck junctures and metal trunnions such as the Stryker
Rejuvenate.
Although pseudotumors are not
cancerous and do not indicate infection, they can nonetheless be quite serious,
causing local tissue destruction. In many cases revision surgery will be
necessary during the removal of the pseudotumor. Both the Rejuvenate and the
ABG II were part of the Stryker hip replacement recall in July of 2012 due to
fretting, corrosion, implant failure and metal poisoning. When the implant is
subject to corrosion, microscopic shards of metals are released into the hip
tissues as well as the bloodstream. In addition to contributing to the
formation of pseudotumors, this metal debris can cause inflammation, chronic
pain, tissue necrosis, bone loss and symptoms of metal toxicity such as:
·
Gastrointestinal disorders
·
Neurological problems
·
Cardiovascular, renal and thyroid issues
·
Loss of vision and hearing
·
Balance problems and memory loss
·
Depression, anxiety and irritability
·
Disruption of DNA
One study sought to establish
the relationship between levels of metal ions and presence of pseudotumors in
patients with metal hip implants. An overall prevalence of asymptomatic
pseudotumors of 4-5 percent among those with metal or partial metal hip implant
was noted—higher than previously believed. Pseudotumors were found to be more
common in women, and patients with pseudotumors were found to have
significantly higher levels of cobalt and chromium in their blood and joint
fluid. It appears that pseudotumors could well be a reaction to metal debris
generated by such hip implants as the Stryker Rejuvenate as well as other metal
hip implant devices. Patients with unusual hypersensitivity to metals were also
found to have a higher risk of developing pseudotumors.
One doctor investigated the
source of wear in the removed implants among patients with pseudotumors as
compared to implants removed for other reasons. Implants which were replaced
due to the presence of pseudotumors showed much greater wear on the femoral and
acetabular cup components. When femoral components come into contact with the
edge of the acetabular component, edge loading occurred and in this study the
wear on the acetabular cup was always on the edge. The patients with pseudotumors often
experienced edge-loading during walking or other activities while less than one
in four patients without pseudotumors experienced edge-loading.
Surgeons are cautioned to be
alert for the presence of pseudotumors in hip implant recipients even when
x-rays appear normal. Special care should be taken when positioning hip implant
devices in smaller women in order to avoid the occurrence of pseudotumors, and
patients should have regular reassessments. Patients with metal sensitivities
should reconsider implantation with an all-metal or partial metal device in
favor of a ceramic or polyethylene implant. Any unusual pain or swelling
requires an appointment with a physician and possible revision surgery
depending on the size and location of the pseudotumor as well as whether tissue
damage has occurred.
